1. Technical Field
The embodiments in the present disclosure relate to telecommunications terminal apparatuses, base station apparatuses, telecommunications systems, telecommunications methods and integrated circuits, for efficiently selecting network cells for camping terminals.
In the 3rd Generation Partnership Project (3GPP), which is a standardization project, by adopting the orthogonal frequency-division multiplexing (OFDM) communications scheme and flexible scheduling by predetermined frequencies and time units, called resource blocks, the standardization of Evolved Universal Terrestrial Radio Access (E-UTRA), realizing high-speed telecommunications, is being carried out. S-UTRA is sometimes also referred to as Long Term Evolution (LTE).
Also, with 3GPP, studies of LTE Advanced (also referred to as LTE-A), realizing higher-speed data transfer and possessing upper-level compatibility with respect to LTE, are underway.
With LTE Advanced, studies involving low-cost wireless terminal apparatuses using machine-type communication (MTC) or machine-to-machine communication (M2M) are being carried out (Non-Patent Document 1). In the following, wireless terminal apparatuses as well as telecommunications apparatuses designed for MTC/M2M and having cost-lowering functionality and/or functionality for supporting coverage enhancement will also be referred to as machine-type communication user equipment (MTCUE). Nevertheless, these types of wireless terminal applications are not limited to machine-type communication or machine-to-machine communication.
In 3GPP, proposals have been made in order to realize low-cost MTCUE including band narrowing of transmit/receive bandwidth, reduction of antenna port numbers/RF tuning numbers, reduction of transmit/receive data transmission rates, adoption of half-duplex frequency division duplex schemes, reduction of transmit/receive power, and prolongation of discontinuous reception intervals. Also, as means of realizing low-cost MTCUE, proposals have been made including reduction of maximum bandwidth in transmit/receive RF circuits and transmit/receive base-band circuits for MTCUE.
Meanwhile, in order to compensate for deterioration in reception/transmission qualities due to the impact of, for example, a reduction in the number of antenna ports, ideas such as repeatedly transmitting to the MTCUE the downlink data or the downlink signal for a one-time data transmission, or the MTCUE repeatedly transmitting to the base station apparatus the uplink data or the uplink signal for a one-time data transmission have been considered.
Furthermore, not only studies for cost-lowering, but also coverage-enhancement and coverage-improvement studies for enhancing the MTCUE transmit/receive range, or coverage, have been made. For example, the enhancing of coverage for spaces such as subterranean rooms, which have been an out of transmission-area due to the large signal attenuation, has been studied to date. For the sake of coverage enhancement, the base station repeatedly transmitting downlink data or downlink signals to the MTCUE, or the MTCUE repeatedly transmitting uplink data or uplink signals to the base station apparatus have been considered (Non-Patent Document 2).
For example, the base station repeats transmission on the physical reporting (broadcast) channel (PBCH) to the MTCUE multiple times within 40 ms. Further, in a random-access procedure the MTCUE repeatedly transmits the same random-access preamble using multiple resources on the physical random-access channel (PRACH). The base station that has received the random-access preamble repeatedly transmits a random-access response message. Here, the base station notifies cell-internal MTCUE of the number of repetitions (the number of attempts) using system information, and otherwise reports to the MTCUE individually (Non-Patent Document 2).
One challenge with enhancement of coverage has been that because it is synonymous with extending conventional cell areas, if criteria for conventional cell-selection and cell-reselection evaluation are followed, a cell in question may be determined to be out-of-service area due to low measurement quality, such that the cell cannot be camped on. Further, only the cells that support coverage enhancement may be accessible by the wireless terminal due to its low-cost functionality, and this issue ought to be considered during the cell selection or cell reselection process. These challenges remain unsolved.
2. Background Literature